Mercurial > jdk8-mips64-public > langtools / file revision

 /*

  * Copyright (c) 1999, 2005, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 package com.sun.tools.javac.util;

 /** A class for extensible, mutable bit sets.

  *

  *  <p><b>This is NOT part of any supported API.

  *  If you write code that depends on this, you do so at your own risk.

  *  This code and its internal interfaces are subject to change or

  *  deletion without notice.</b>

  */

 public class Bits {

     private final static int wordlen = 32;

     private final static int wordshift = 5;

     private final static int wordmask = wordlen - 1;

     private int[] bits;

     /** Construct an initially empty set.

      */

     public Bits() {

         this(new int[1]);

     }

     /** Construct a set consisting initially of given bit vector.

      */

     public Bits(int[] bits) {

         this.bits = bits;

     }

     /** Construct a set consisting initially of given range.

      */

     public Bits(int start, int limit) {

         this();

         inclRange(start, limit);

     }

     private void sizeTo(int len) {

         if (bits.length < len) {

             int[] newbits = new int[len];

             System.arraycopy(bits, 0, newbits, 0, bits.length);

             bits = newbits;

         }

     }

     /** This set = {}.

      */

     public void clear() {

         for (int i = 0; i < bits.length; i++) bits[i] = 0;

     }

     /** Return a copy of this set.

      */

     public Bits dup() {

         int[] newbits = new int[bits.length];

         System.arraycopy(bits, 0, newbits, 0, bits.length);

         return new Bits(newbits);

     }

     /** Include x in this set.

      */

     public void incl(int x) {

         assert x >= 0;

         sizeTo((x >>> wordshift) + 1);

         bits[x >>> wordshift] = bits[x >>> wordshift] |

             (1 << (x & wordmask));

     }

     /** Include [start..limit) in this set.

      */

     public void inclRange(int start, int limit) {

         sizeTo((limit >>> wordshift) + 1);

         for (int x = start; x < limit; x++)

             bits[x >>> wordshift] = bits[x >>> wordshift] |

                 (1 << (x & wordmask));

     }

     /** Exclude x from this set.

      */

     public void excl(int x) {

         assert x >= 0;

         sizeTo((x >>> wordshift) + 1);

         bits[x >>> wordshift] = bits[x >>> wordshift] &

             ~(1 << (x & wordmask));

     }

     /** Is x an element of this set?

      */

     public boolean isMember(int x) {

         return

             0 <= x && x < (bits.length << wordshift) &&

             (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;

     }

     /** this set = this set & xs.

      */

     public Bits andSet(Bits xs) {

         sizeTo(xs.bits.length);

         for (int i = 0; i < xs.bits.length; i++)

             bits[i] = bits[i] & xs.bits[i];

         return this;

     }

     /** this set = this set | xs.

      */

     public Bits orSet(Bits xs) {

         sizeTo(xs.bits.length);

         for (int i = 0; i < xs.bits.length; i++)

             bits[i] = bits[i] | xs.bits[i];

         return this;

     }

     /** this set = this set \ xs.

      */

     public Bits diffSet(Bits xs) {

         for (int i = 0; i < bits.length; i++) {

             if (i < xs.bits.length) {

                 bits[i] = bits[i] & ~xs.bits[i];

             }

         }

         return this;

     }

     /** this set = this set ^ xs.

      */

     public Bits xorSet(Bits xs) {

         sizeTo(xs.bits.length);

         for (int i = 0; i < xs.bits.length; i++)

             bits[i] = bits[i] ^ xs.bits[i];

         return this;

     }

     /** Count trailing zero bits in an int. Algorithm from "Hacker's

      *  Delight" by Henry S. Warren Jr. (figure 5-13)

      */

     private static int trailingZeroBits(int x) {

         assert wordlen == 32;

         if (x == 0) return 32;

         int n = 1;

         if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }

         if ((x & 0x00ff) == 0) { n +=  8; x >>>=  8; }

         if ((x & 0x000f) == 0) { n +=  4; x >>>=  4; }

         if ((x & 0x0003) == 0) { n +=  2; x >>>=  2; }

         return n - (x&1);

     }

     /** Return the index of the least bit position >= x that is set.

      *  If none are set, returns -1.  This provides a nice way to iterate

      *  over the members of a bit set:

      *  <pre>

      *  for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...

      *  </pre>

      */

     public int nextBit(int x) {

         int windex = x >>> wordshift;

         if (windex >= bits.length) return -1;

         int word = bits[windex] & ~((1 << (x & wordmask))-1);

         while (true) {

             if (word != 0)

                 return (windex << wordshift) + trailingZeroBits(word);

             windex++;

             if (windex >= bits.length) return -1;

             word = bits[windex];

         }

     }

     /** a string representation of this set.

      */

     public String toString() {

         char[] digits = new char[bits.length * wordlen];

         for (int i = 0; i < bits.length * wordlen; i++)

             digits[i] = isMember(i) ? '1' : '0';

         return new String(digits);

     }

     /** Test Bits.nextBit(int). */

     public static void main(String[] args) {

         java.util.Random r = new java.util.Random();

         Bits bits = new Bits();

         int dupCount = 0;

         for (int i=0; i<125; i++) {

             int k;

             do {

                 k = r.nextInt(250);

             } while (bits.isMember(k));

             System.out.println("adding " + k);

             bits.incl(k);

         }

         int count = 0;

         for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {

             System.out.println("found " + i);

             count ++;

         }

         if (count != 125) throw new Error();

     }

 }